folic acid headaches?

I switched to a different folic acid(different brand) a couple of days ago(and admittedly didn't always take my old ones every day) and now I get headaches about three hours after I take it.Has anybody else experienced that?

I'm g/c from planning, hope you don't mind. I've noticed that since I've been taking folic acid I've been getting headaches quite regularly. I take folic acid at night as I'd heard it could cause nausea, but quite often I've been waking up with a headache. Not entirely sure whether it's the folic acid or stress though!